Method And Apparatus For Unifying An Epon Access Network And A Coax-Based Access Network

ABSTRACT

Methods and systems for unifying an EPON network and a coax-based access network may include, in a network with an Ethernet passive optical network (EPON) optical line terminal (OLT), coaxial network units (CNUs), and an optical coax bridge (OCB) with a plurality of virtual optical network units (vONUs) each comprising a plurality of logical link identifiers (LLIDs) and having its own MAC address, each vONU corresponding to one CNU: forming, in the OCB, each of the plurality of vONUs when a respective CNU is admitted to a coax network coupled to the OCB; communicating data transmissions from an optical fiber network to the coax network, and data transmissions from the coax network to the optical fiber network, via said OCB; and transmitting and receiving data packets between the OLT and the at least one CNU. The OCB may emulate an optical network unit (ONU) relative to the OLT.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Ser. No. 15/881,000 filed on Jan.26, 2018, which is a continuation of application Ser. No. 14/383,623filed on Sep. 8, 2014, which is the National Stage Entry of PCTApplication PCT/US2013/029923, which claims the benefit of U.S.Provisional Application No. 61/608,632, filed Mar. 8, 2012, thespecification of which is incorporated by reference.

FIELD

This disclosure is related to a communication network and moreparticularly to bridging Ethernet passive optical networks with coaxbased access networks.

BACKGROUND INFORMATION

There are two different types of access networks for packet datatransmission. These are shown in FIGS. 1 and 2. FIG. 1 shows a typicalEthernet passive optical network (EPON) consisting of an optical lineterminal (OLT) 10 at the headend side of the system. A typical OLT hasmedium access logic 12 connected to transmitter (Tx) 14 and receiver(Rx) 16 that is connected to wavelength division multiplexer (WDM) 18.The data packets are sent and received through optical fiber 20. Opticalfiber 20 is connected to 1:N optical splitter 22 which is dispersed to aplurality of optical network units (ONUs) 24 on the customer premisesside.

A second type of access network is shown in FIG. 2. This is a coaxialcable-based access network. In this system access network controller 26at the headend side, is linked by coaxial cable 28 to a plurality ofcoax networks units (CNUs) 30 at the customer premises side.

SUMMARY

The embodiments disclosed herein are for a multi-system operator (MSO)to deploy a standard OLT and install ONUs so the MSO can connect ONUs tothe OLT to via an optical fiber. For users that do not have access to anoptical fiber, the MSO deploys a converter between the optical fiber anda coax network so that the MSO can use the standard OLT to communicatewith CNUs.

The following presents a simplified summary of one or more embodimentsin order to provide a basic understanding of some aspects of suchembodiments. This summary is not an extensive overview of the one ormore embodiments, and is intended to neither identify key or criticalelements of the embodiments nor delineate the scope of such embodiments.Its sole purpose is to present some concepts of the describedembodiments in a simplified form as a prelude to the more detaileddescription that is presented later.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed method and apparatus, in accordance with one or morevarious embodiments, is described with reference to the followingfigures. The drawings are provided for purposes of illustration only andmerely depict examples of some embodiments of the disclosed method andapparatus. These drawings are provided to facilitate the reader'sunderstanding of the disclosed method and apparatus. They should not beconsidered to limit the breadth, scope or applicability of the claimedinvention. It should be noted that for clarity and ease of illustration,these drawings are not necessarily made to scale.

FIG. 1 is an illustration of an EPON in an optical access networkconsisting of an optical line terminal (OLT) at the headend side andseveral (i.e., N) optical network units (ONUs) at the customer premiseside.

FIG. 2 illustrates a coaxial cable-based access network.

FIG. 3 illustrates an embodiment of the disclosed method and apparatusin which the same OLT is used for both customers that are reachablethrough optical fiber, and those that are not reachable through opticalfiber, but are reachable through coaxial cable.

FIG. 4 is an illustration of an embodiment in which a standard EPONaccess network is connected to a coaxial cable access network, throughan optical fiber to coax bridge (OCB: Optical-to-Coax Bridge) device.

The figures are not intended to be exhaustive or to limit the claimedinvention to the precise form disclosed. It should be understood thatthe disclosed method and apparatus can be practiced with modificationand alteration, and that the invention should be limited only by theclaims and the equivalents thereof.

DETAILED DESCRIPTION

The presently claimed invention solves the problem of the ability ofusing a standard OLT to communicate with both ONUs and CNUs without theOLT having to distinguish the difference between the network units.

Disclosed is a MSO deploying a standard OLT, and installed with ONUs tobe used by customers to whom the MSO can connect using optical fiber.For customers that cannot be reached with optical fiber, the MSO deploysa converter between the optical fiber and the coax cable network so thatthe MSO can use the same standard OLT, and use CNUs for those customersattached to the coax cable network.

FIG. 3 shows one embodiment whereby the same OLT 10 is used for bothtypes of customers, those who are reachable through optical fiber, andthose who are not reachable through optical fiber, but are reachablethrough coaxial cable, such as Entropic Communications' c.Link accessnetwork, via a pass-through device that passes data between the OLT 10and at least one CNU. This pass-through device preferably is flexible inseveral ways, such as allowing the MSO to use different portions of theRF spectrum, including more or less spectrum as available. Additionally,for the OLT, the behavior of a CNU must be functionally equivalent oremulates an ONU so that the OLT does not know the difference. This isachieved by the pass-through device that translates the behaviors of theCNUs into that of one or plural ONUs relative to the OLT, and translatesthe behaviors of the OLT into that of the coax network's networkcoordinator. Further, for interoperability between different vendors, itis desirable for a standard to exist that governs how this pass-throughdevice and the CNUs work.

A standard EPON access network is connected to a coaxial cable accessnetwork through optical fiber 20 to coax bridge, such asoptical-fiber-to-coax bridge (OCB) 34. In this embodiment, OLT 10 ispreferably a standard EPON OLT. This embodiment is used when there aretwo types of devices at customer premises, a first type is a standardEPON ONU, used for customers who can be reached by optical fiber, andthe second type is a coaxial cable-based access CNU, which includesc.LINK access CPE, DOCSIS Cable Modem CPE, WiFi Station, and the like.First, an optical splitter 22 provides access to each of the pluralityof ONUs 48 which operate in the normal fashion. Optical splitter 22 alsoprovides access to at least one OCB 34. Optical-fiber-to-coax bridge orOCB 34 device preferably has an ONU port 36 and coax port 38. A networkcoordinator (NC) 40 of the coaxial cable access network (or equivalentlythe CMTS of the DOCSIS network, or Access Point of the WiFi network),manages the regular operation of the coaxial cable access network, likenode admission, TDMA scheduling, etc. Relative to the standard OLT, OCB34 behaves as a standard ONU 40, with multiple LLIDs 44. For each CNU 46(i.e. a cable CPE), OCB 34 creates a set of LLIDs 44. There can be oneor more LLIDs in a set. Thus, the OCB's ONU port 36 has M sets of LLIDs44, which represents M CNUs 45. For example, a coaxial access networkwith M CNUs 45, OCB 34 will thus create M sets of LLIDs 44.

For downstream traffic from OLT 10, OCB 34 receives all the packets, butwill discard those packets whose LLIDs 44 and destination MAC address donot belong to this OCB 34, and will store the packets that are destinedto this OCB 34 and/or the CNUs 46. Concurrently, OCB 34 schedules andtransmits downstream packets to CNUs 46, following the protocol of thecoaxial cable access network, like c.LINK.

For upstream traffic from CNUs 46 to OCB 34, the OCB schedules them andreceives them, following the protocol of the coaxial cable accessnetwork, like c.LINK. Concurrently, OCB 34 uses REPORT messages torequest EPON bandwidth for individual LLIDs 44 and queues to OLT 10, andthe OLT uses GATE messages to grant time slots for individual LLIDs 44and queues. Upon receiving GATE messages, OCB 34 transmits packets forappropriate LLIDs 44 and queues. For EPON admission/registration, OCB 34will register the OCB's ONU port 36 as if it is a standard ONU 48, withall the LLIDs 44 needed to support all the CNUs 46 of the coaxial cableaccess network.

For network provisioning and management, data over cable serviceinterface specification (DOCSIS) provisioning of EPON (DPoE) can be useddirectly. OLT 10 considers the ONU port 36 of OCB 34 as if it is astandard ONU 48. For whatever operations that OLT 10 performs, the logicONU and the OCB 34 will translate them into corresponding operations inthe coaxial cable access network, and report back results whenappropriate. In this respect, logically ONU port 36 is considered as theDPoE API of a standard ONU 48, and the coaxial cable network operationsis considered as the actual execution of the DPoE operations inside astandard ONU device.

A second embodiment of an OCB device is shown in FIG. 4. Like theembodiment of FIG. 1, this embodiment has an OLT 10 with all of theinclusions of FIG. 1. As in the previous embodiment, an optical splitter22 provides access to each of the plurality of ONUs 62 which operate inthe normal fashion. Optical splitter 22 also provides access to at leastone OCB 60. In this embodiment, each OCB has an ONU port 50 and coaxport 52. It is the network coordinator (NC) 54 of the coaxial cableaccess network, (or equivalently the CMTS of the DOCSIS network, orAccess Point of the WiFi network), managing the regular operation of thecoaxial cable access network, like node admission, TDD scheduling, etc.Relative to a standard OLT 10, the OCB's ONU port 50 behaves as Mvirtual ONUs 56, each with one or multiple LLIDs, where M is the numberof CNUs 58 in the coaxial cable access network. M virtual ONUs 56 areco-located at the same physical location in the OCB 60. Each virtual ONU64 has its own MAC address, and is uniquely mapped to a CNU for dataflows.

For downstream traffic from OLT 10, OCB 60 receives and stores thepackets for each virtual ONU 56 and discards packets that are notdestined to any of the virtual ONUs 56 and concurrently, OCB 60schedules and transmits downstream packets to CNUs 58, following theprotocol of the coaxial cable access network, like c.LINK.

For upstream traffic from CNUs 58 to OCB 60, the OCB schedules them andreceives them from CNUs 58, following the protocol of the coaxial cableaccess network, like c.LINK and concurrently, OCB 60 uses REPORTmessages to request EPON bandwidth for individual virtual ONUs 56 andtheir respective LLIDs and queues to OLT 10. The OLT uses GATE messagesto grant time slots for individual virtual ONUs 64 and their respectiveLLIDs and queues. Upon receiving GATE messages, the OCB transmit packetsfor appropriate ONUs (and LLIDs and queues). For EPON admission, OCB 10will register each virtual ONU 64 separately as if it is a standard realONU 62. Virtual ONU 64 is formed by OCB 10 when a CNU 58 is admittedinto the coaxial cable access network by the OCB's NC 54 entity. Fornetwork provisioning and management, DPoE can be used directly. OLT 10considers M virtual ONUs 56 in the OCB as if they are standard ONUs 62.For whatever operations that OLT 10 performs on each virtual ONU 56, theOCB will translate them into corresponding operations in the coaxialcable access network, and report back results when appropriate. In thisrespect, a virtual ONU is considered as the DPoE API of a standard ONU,and the coaxial cable network operations are considered as the actualexecution of the DPoE operations inside a standard ONU device.

The introduction of ONU port 50 and virtual ONUs 56 effectivelydissociates the optical fiber network segment and the coaxial cablenetwork segment. The two networks thus operate concurrently butasynchronously. The OLT scheduler does not need to distinguish virtualONUs 56 from standard ONUs 62. In fact, the OLT does not need to beaware that there is coaxial cable access network connected to the EPONsystem. There is no constraint on wire speed for any of the two networksegments. The queue buffers in the OCB can be implemented in variousways depending on the number of CNUs supported, the speed, throughput,and latency of the coaxial cable access network. The OCB can do dataflow control between the OLT and the CNUs by coordinating the differentdata flow control mechanisms between the OLT and the OCB (emulated ONU,or ONUs), and between the NC and the CNUs.

Note that with this architecture, the coaxial cable access network maybe replaced by any other networks, like a c.LINK network, a new coaxialcable based network to be standardized, a WiFi network where the APtakes the place of the NC in the OCB, a DOCSIS network where theCMTS/headend replace the NC in the OCB, a HomePlug network, a HPNAnetwork, a G.Hn network or any similar type network.

In the prior art or known systems, there are several shortcomings thathave been overcome by the presently claimed invention. They include, astandard EPON OLT has no definition or awareness of a coaxial mediaconverter (CMC), so there is an issue of doing network provisioning andmanagement by DPoE. Additionally, framing, modulation, and forward errorcorrection (FEC) on optical fiber needs to be different from framing oncoax because of physical channel difference. 1G-EPON adopts optionalframe-based FEC. When the FEC is not used in EPON, either the coaxsegment will suffer serious packet error rate or the CMC will need toadd FEC for the coax segment, which increases the latency, and requiresthe CMC to first recover the packets and then add FEC. 10G-EPON usesmandatory stream-based FEC where parity symbols generated after eachdata block are inserted immediately after the FEC parity codeword thatthey are protecting, resulting in an interleaving pattern of data blocksand parity blocks. Because the coax segment typically has a lowerthroughput, the CMC must first do the reverse FEC, discard packets notneeded, and then re-do FEC for the needed packets and silence stream. Ifthe speed on coax is different than on fiber, and standard OLT isunaware of such a thing, there are problems because of the very lowlatency between the GATE message and the allocated transmission slot.The minimum time interval from the Grant message to the allocatedtransmit time is 1024×16 ns. This latency is easily exceeded by the CMC.Since all packets between the OLT and the CNUs pass through CMC, the OLTmay need to instruct CMC how traffic between the CMC and CNUs must becoordinated, but current OLT is not aware of CMC. Ranging between theOLT and the CNU must get coordination from CMC. There is different needfor power control in optical segment and the coaxial cable segment, CMCneeds to get involved.

The virtual ONU concept disclosed in this filing effectively avoids allthese problems, and still enables network provisioning through DPoE.Each network segment (optical and coaxial) can use the PHY and MACmechanisms best suited for that medium.

While various embodiments of the disclosed method, apparatus, andcomputer program have been described above, it should be understood thatthey have been presented by way of example only, and should not limitthe claimed invention. Embodiments of the claimed invention may beimplemented in method steps, hardware, firmware, software, or anycombination thereof. Embodiments of the invention may also beimplemented as non-transitory computer-executable storage medium.Likewise, the various diagrams may depict an example architectural orother configuration for the disclosed method and apparatus. This is doneto aid in understanding the features and functionality that can beincluded in the disclosed method, apparatus, and computer program. Theclaimed invention is not restricted to the illustrated examplearchitectures or configurations, rather the desired features can beimplemented using a variety of alternative architectures andconfigurations. Indeed, it will be apparent to one of skill in the arthow alternative functional, logical or physical partitioning andconfigurations can be implemented to implement the desired features ofthe disclosed method and apparatus. Also, a multitude of differentconstituent module names other than those depicted herein can be appliedto the various partitions. Additionally, with regard to flow diagrams,operational descriptions, and method claims, the order in which thesteps are presented herein shall not mandate that various embodiments beimplemented to perform the recited functionality in the same orderunless the context dictates otherwise.

Although the disclosed method and apparatus is described above in termsof various exemplary embodiments and implementations, it should beunderstood that the various features, aspects and functionalitydescribed in one or more of the individual embodiments are not limitedin their applicability to the particular embodiment with which they aredescribed. Thus, the breadth and scope of the claimed invention shouldnot be limited by any of the above-described exemplary embodiments.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as meaning “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof, the terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike; and adjectives such as “conventional,” “traditional,” “normal,”“standard,” “known” and terms of similar meaning should not be construedas limiting the item described to a given time period or to an itemavailable as of a given time, but instead should be read to encompassconventional, traditional, normal, or standard technologies that may beavailable or known now or at any time in the future. Likewise, wherethis document refers to technologies that would be apparent or known toone of ordinary skill in the art, such technologies encompass thoseapparent or known to the skilled artisan now or at any time in thefuture.

A group of items linked with the conjunction “and” should not be read asrequiring that each and every one of those items be present in thegrouping, but rather should be read as “and/or” unless expressly statedotherwise. Similarly, a group of items linked with the conjunction “or”should not be read as requiring mutual exclusivity among that group, butrather should also be read as “and/or” unless expressly statedotherwise. Furthermore, although items, elements or components of thedisclosed method and apparatus may be described or claimed in thesingular, the plural is contemplated to be within the scope thereofunless limitation to the singular is explicitly stated.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “module” does not imply that the components or functionalitydescribed or claimed as part of the module are all configured in acommon package. Indeed, any or all of the various components of amodule, whether control logic or other components, can be combined in asingle package or separately maintained and can further be distributedin multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described interms of exemplary block diagrams, flow charts, and other illustrations.As will become apparent to one of ordinary skill in the art afterreading this document, the illustrated embodiments and their variousalternatives can be implemented without confinement to the illustratedexamples. For example, block diagrams and their accompanying descriptionshould not be construed as mandating a particular architecture orconfiguration.

Several embodiments are specifically illustrated and/or describedherein. However, it will be appreciated that modifications andvariations of the disclosed embodiments are covered by the aboveteachings and within the purview of the appended claims withoutdeparting from the spirit and intended scope of the invention.

What is claimed is:
 1. A method of communication, the method comprising:in a network comprising an Ethernet passive optical network (EPON)optical line terminal (OLT), a plurality of coaxial network units(CNUs), and an optical coax bridge (OCB) comprising a plurality ofvirtual optical network units (vONUs) each comprising a plurality oflogical link identifiers (LLIDs) and having its own MAC address, eachvONU corresponding to one CNU: forming, in the OCB, each of theplurality of vONUs when a respective CNU is admitted to a coax networkcoupled to the OCB; communicating data transmissions between an opticalfiber network and the coax network via said OCB; and communicating datapackets between the OLT and at least one CNU.
 2. The method of claim 1wherein the OCB-performs one or more of: emulating an optical networkunit (ONU) relative to the OLT; filtering out any data packets from theOLT that are not destined to any of the OCB LLIDs, and keeping andforwarding all data packets that are destined for any of the OCB LLIDs;controlling the coax network and managing the operation of the coaxnetwork; receiving the data packets by the OCB from the OLT, storingdestined data packets, scheduling time-slots on the coax network, andtransmitting the destined data packets to an appropriate CNU; receivingdata packets from the at least one CNU, storing the data packetsaccording to the corresponding LLIDs, requesting the OLT fortransmission time-slots, waiting for the scheduled time-slots from theOLT, and transmitting the data packets to the OLT; and operating withvarying portions of an RF spectrum.
 3. A system for communication, thesystem comprising: an Ethernet passive optical network (EPON) opticalline terminal (OLT), a plurality of coaxial network units (CNUs), and anoptical coax bridge (OCB) coupled to the CNU and comprising a pluralityof virtual optical network units (vONUs) each comprising a plurality oflogical link identifiers (LLIDs) and having its own MAC address, eachvONU corresponding to one CNU, said OCB being operable to: form, in theOCB, each of the plurality of vONUs when a respective CNU is admitted toa coax network coupled to the OCB; communicate data transmissionsbetween an optical fiber network and the coax network; and communicatedata packets between the OLT and at least one CNU.
 4. The system ofclaim 3 wherein the OCB is operable to perform one or more of: emulatingan optical network unit (ONU) relative to the OLT; filtering out anydata packets from the OLT that are not destined to any of the OCB LLIDs,and keeping and forwarding data packets that are destined for any of theOCB LLIDs; controlling the coax network and managing the operation ofthe coax network; receiving all the data packets from the OLT, storingdestined data packets, scheduling time-slots on the coax network andtransmitting the destined data packets to an appropriate CNU; andreceiving data packets from the at least one CNU, storing the datapackets according to the corresponding LLIDs, requesting the OLT fortransmission time-slots, waiting for the scheduled time-slots from theOLT, and transmitting the data packets to the OLT wherein the OCBcomprises a flexible OCB for operating with varying portions of an RFspectrum.
 5. A method of data communication, the method comprising: in anetwork comprising an Ethernet passive optical network (EPON) opticalline terminal (OLT), a plurality of coaxial network units (CNUs), and anoptical coax bridge (OCB) comprising a plurality of virtual opticalnetwork units (vONUs) each comprising a plurality of logical linkidentifiers (LLIDs) and having its own MAC address, each vONUcorresponding to one CNU: forming, in the OCB, each of the plurality ofvONUs when a respective CNU is admitted to a coax network coupled to theOCB; communicating data transmissions between an optical fiber networkand the coax network via said optical coax bridge (OCB); andcommunicating data packets between the OLT and the respective CNU. 6.The method of claim 5, comprising filtering out, by the OCB, any datapackets from the OLT that are not destined to any of the OCB vONUs, andkeeping and forwarding data packets that are destined for any of the OCBvONUs.
 7. The method of claim 5, comprising receiving data packetsdestined to any of the vONUs emulated by the OCB, by the OCB from theOLT, storing the received destined data packets, scheduling time-slotson the coax network and transmitting the data packets to an appropriateCNU.
 8. The method of claim 5, comprising receiving data packets from atleast one CNU by the OCB that are destined to the OLT, storing the datapackets according to the corresponding vONUs and its associated LLIDs,requesting the OLT for transmission time-slots, waiting for thescheduled time-slots from the OLT and transmitting the data packets tothe OLT.
 9. The method of claim 5, wherein the OCB comprises a flexibleOCB for operating with varying portions of an RF spectrum.
 10. A systemfor data communication, the system comprising an Ethernet passiveoptical network (EPON) optical line terminal (OLT), a plurality ofcoaxial network units (CNUs), and an optical coax bridge (OCB)comprising a plurality of virtual optical network units (vONUs) eachcomprising a plurality of logical link identifiers (LLIDs) and havingits own MAC address, each vONU corresponding to one CNU, the OCB beingoperable to: form, in the OCB, each of the plurality of vONUs when arespective CNU is admitted to a coax network coupled to the OCB;communicate data transmissions between an optical fiber network and thecoax network via an optical coax bridge (OCB); and communicate datapackets between the OLT and at least one CNU.
 11. The system of claim10, wherein the system comprises one or both of: a filter for filteringout any data packets from the OLT that are not destined to any of theOCB vONUs, and keeping and forwarding data packets that are destined forany of the OCB vONUs; and a controller for controlling the coax networkand managing the operation of the coax network by the OCB, the OCB beingoperable to: receive the data packets destined to any of the vONUsemulated by the OCB from the OLT; store the received destined datapackets; schedule time-slots on the coax network; transmit the datapackets to an appropriate CNU; receive data packets from the at leastone CNU that are destined to the OLT; store the data packets accordingto the corresponding vONUs and its associated LLIDs; request the OLT fortransmission time-slots; and wait for the scheduled time-slots from theOLT and transmit the data packets to the OLT.
 12. A method of datacommunication, the method comprising: in a network comprising anEthernet passive optical network (EPON) optical line terminal (OLT), atleast one second network, and an optical coax bridge (OCB) comprising aplurality of virtual optical network units (vONUs) each comprising aplurality of logical link identifiers (LLIDs) and having its own MACaddress, each vONU corresponding to one coaxial network unit (CNU):forming, in the OCB, each of the plurality of vONUs when a respectiveCNU is admitted to a second access medium network coupled to the OCB;communicating data transmissions between the first access networkcomprising an optical fiber network and the second access medium networkvia said OCB; and communicating data packets between the OLT and thenetwork unit of the second access medium network.
 13. The method ofclaim 12 wherein the second access network comprises a member from thegroup consisting of a c.LINK network, a standardized coaxial cable basednetwork, a WiFi network, a DOCSIS network, a HomePlug network, a HPNAnetwork, and a G.Hn network.
 14. The method of claim 12, comprisingcontrolling, by the OCB, a coax network and managing the operation ofthe coax network.
 15. The method of claim 12, comprising receiving alldata packets destined to any of the vONUs emulated by the OCB, by theOCB from the OLT, storing the received destined data packets, schedulingtime-slots on a coax network and transmitting the data packets to anappropriate CNU.
 16. The method of claim 12, comprising receiving datapackets from at least one CNU by the OCB that are destined to the OLT,storing the data packets according to the corresponding vONUs and itsassociated LLIDs, requesting the OLT for transmission time-slots,waiting for the scheduled time-slots from the OLT and transmitting thedata packets to the OLT.
 17. The method of claim 12, wherein the OCBcomprises a flexible OCB for operating with varying portions of an RFspectrum.